All modern dental units have a water supply that provides coolant and rinse water to the dynamic dental instruments including the high-speed handpiece, air/water syringe and ultrasonic scaler. This water supply is connected to a domestic water source system. Microbiological studies of this water supply revealed that the water is contaminated by water organisms and oral flora. These organisms have been found to be massive in number and some identified as pathogenic. Dental researchists have stated that this contamination could cause infection in immuno-suppressed patients, and cross infection may occur between dental patients.
Clinical tests show that oral flora is aspirated from a patient's oral cavity into the dental unit water lumens through the dynamic dental instruments. This revelation has prompted the Centers of Disease Control to recommend a 20 to 30 second purge of these instruments between each patient appointment. The American Dental Association and The American National Standards Institute developed Specification Number 47, dated Apr. 12, 1984, as the manufacturing criterion for dental unit manufacturers. This specification requires that a means be incorporated in the dental unit to prevent water from being drawn back beyond the point of the dental instrument connection. These are attempts to improve the quality of water used for dental treatment. However, continuing research indicates that neither has significantly reduced contamination.
Medical studies have determined that disease incubation periods vary. Because of this variance it is difficult to make accurate assessments as to the time and place of infection. Dental treatment is frequently subgingival and invasive of the mucosa therefore providing a direct access to the vascular system. It is therefore prudent to use microbiologically pure water for cooling and rinsing during dental treatment in lieu of water considered by public health standards to be polluted and nonpotable.
Biofilms are defined as microbial masses attached to surfaces that are bathed in liquids, such as dental unit tubing. Organisms grow in organized structures with channels in between, similar to a vascular system. The biofilm remains attached as water flows through the dental unit tubing. However, some microbes in the biofilm may be periodically released into the flowing fluid where they can be transported to the outlet of the line, e.g., the air/water syringe or spray handpiece. Examples of microbes found in dental unit water lines include species of waterborne pseudomonas, legionella, klebsiella, moraxella, bacillus, flavobacterium, and escheria as well as organisms common to the oral environment. Thus, biofilms can continually contaminate water flowing through a dental unit line.